alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Matryoshka CnC Beacon 2"; flow:established,to_server; urilen:>50; http.method; content:"GET"; http.uri; content:"/img/"; startswith; fast_pattern; content:"/"; distance:32; within:1; content:"/n"; distance:0; content:".png"; endswith; pcre:"/^\/img\/[a-f0-9]{32}\/[a-f0-9]+\/n\d+\.png$/"; http.header_names; to_lowercase; content:!"|0d 0a|referer|0d 0a|"; reference:md5,9853fc1f4d7ba23d728f4ee80842faf9; reference:url,minerva-labs.com/#!CopyKittens-Attack-Group/c7a5/5655651e0cf20a760c4cae95; classtype:command-and-control; sid:2022147; rev:5; metadata:attack_target Client_Endpoint, created_at 2015_11_25, deployment Perimeter, signature_severity Major, tag c2, updated_at 2024_04_27, mitre_tactic_id TA0010, mitre_tactic_name Exfiltration, mitre_technique_id T1041, mitre_technique_name Exfiltration_Over_C2_Channel;)